Pub Date : 2024-01-12DOI: 10.2113/2024/lithosphere_2023_272
Urs S. Klötzli, Bernhard Neugschwentner, Jolanta Burda, Pitsanupong Kanjanapayont, Qiu-Li Li, Yu Liu, Patrik Konečný, Punya Charusiri
The Khanom Core Complex in Peninsular Thailand is a part of the crystalline basement of Sundaland and plays a key role in our understanding of the evolution of Thailand and SE Asia. The complex comprises ortho- and paragneisses, schists, meta-volcanics, subordinate calcsilicate rocks, and postkinematic granitoids. New petrochronological data reveal that the sedimentation and metamorphism of the paragneiss precursors (Haad Nai Phlao complex, Khao Yoi paragneisses) occurred in the Late Cambrian at the latest. A syn- to postsedimentary andesitic intrusion/extrusion in the Haad Nai Phlao complex at 495 ± 10 Ma defines a minimum age for the former event(s). In the Early Ordovician (477 ± 7 Ma), the Haad Nai Phlao complex and the Khao Yoi paragneisses were intruded by the Khao Dat Fa granite. During the Indosinian orogenic events, the Laem Thong Yang (211 ± 2 Ma) and Haad Nai Phlao (210 ± 2 Ma) granitoid plutons were intruded. Immediately afterward (ca. 208–205 Ma), the first metamorphic overprinting of the Laem Thong Yang granite and the Haad Nai Phlao complex including the Khao Dat Fa granite occurred. A second metamorphic overprinting of all lithological units and the contemporaneous intrusion of the Khao Pret granite followed in the Late Cretaceous and Early Paleogene (ca. 80–68 Ma). The tectonic formation of the core complex took place in the Eocene (<42 Ma), followed by exhumation and regional cooling below ca. 450°C and the latest cooling to ca. 120°C in the Miocene (ca. 20 Ma). The evolutionary data show that the Khanom Core Complex is part of Sibumasu, and its Late Cretaceous-Neogene cooling pattern and exhumation history can be directly related to the northward drift of India.Thailand is located on the geological entity known as Sundaland, which consists of Gondwana-derived continental terranes that accreted over time to build the present-day mainland of Indochina [1, 2]. Two main continental terranes can be distinguished, Sibumasu in the west and Indochina in the east, along with an interjacent arc, called Sukhothai. Both terranes are crucial to understand the geological evolution of Gondwana, the various Tethys oceanic domains, Sundaland, and Southeast Asia. However, there is no agreement on the nature and exact locations of their boundaries, the characteristics of the basement evolution, or the tectonic models of their amalgamation (References [2-5] and references therein). This problem is accentuated by the scarcity of crystalline basement exposures. The available basement data are limited to three regions of exposure in northern and southeast Thailand and on the Thai peninsula.The first description of crystalline basement rocks in Thailand was published by Heim and Hirschi [6]. These rocks are typically high- to medium-temperature low-pressure metamorphic and intermediate to acidic plutonic rocks [1, 7, 8]. Often, they are overlain by fossiliferous Phanerozoic sediments [1, 9]. Consequently, the first to assign a Precambrian age to the g
{"title":"The Late Cambrian to Neogene Evolution of the Khanom Core Complex (Peninsular Thailand)","authors":"Urs S. Klötzli, Bernhard Neugschwentner, Jolanta Burda, Pitsanupong Kanjanapayont, Qiu-Li Li, Yu Liu, Patrik Konečný, Punya Charusiri","doi":"10.2113/2024/lithosphere_2023_272","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_272","url":null,"abstract":"The Khanom Core Complex in Peninsular Thailand is a part of the crystalline basement of Sundaland and plays a key role in our understanding of the evolution of Thailand and SE Asia. The complex comprises ortho- and paragneisses, schists, meta-volcanics, subordinate calcsilicate rocks, and postkinematic granitoids. New petrochronological data reveal that the sedimentation and metamorphism of the paragneiss precursors (Haad Nai Phlao complex, Khao Yoi paragneisses) occurred in the Late Cambrian at the latest. A syn- to postsedimentary andesitic intrusion/extrusion in the Haad Nai Phlao complex at 495 ± 10 Ma defines a minimum age for the former event(s). In the Early Ordovician (477 ± 7 Ma), the Haad Nai Phlao complex and the Khao Yoi paragneisses were intruded by the Khao Dat Fa granite. During the Indosinian orogenic events, the Laem Thong Yang (211 ± 2 Ma) and Haad Nai Phlao (210 ± 2 Ma) granitoid plutons were intruded. Immediately afterward (ca. 208–205 Ma), the first metamorphic overprinting of the Laem Thong Yang granite and the Haad Nai Phlao complex including the Khao Dat Fa granite occurred. A second metamorphic overprinting of all lithological units and the contemporaneous intrusion of the Khao Pret granite followed in the Late Cretaceous and Early Paleogene (ca. 80–68 Ma). The tectonic formation of the core complex took place in the Eocene (<42 Ma), followed by exhumation and regional cooling below ca. 450°C and the latest cooling to ca. 120°C in the Miocene (ca. 20 Ma). The evolutionary data show that the Khanom Core Complex is part of Sibumasu, and its Late Cretaceous-Neogene cooling pattern and exhumation history can be directly related to the northward drift of India.Thailand is located on the geological entity known as Sundaland, which consists of Gondwana-derived continental terranes that accreted over time to build the present-day mainland of Indochina [1, 2]. Two main continental terranes can be distinguished, Sibumasu in the west and Indochina in the east, along with an interjacent arc, called Sukhothai. Both terranes are crucial to understand the geological evolution of Gondwana, the various Tethys oceanic domains, Sundaland, and Southeast Asia. However, there is no agreement on the nature and exact locations of their boundaries, the characteristics of the basement evolution, or the tectonic models of their amalgamation (References [2-5] and references therein). This problem is accentuated by the scarcity of crystalline basement exposures. The available basement data are limited to three regions of exposure in northern and southeast Thailand and on the Thai peninsula.The first description of crystalline basement rocks in Thailand was published by Heim and Hirschi [6]. These rocks are typically high- to medium-temperature low-pressure metamorphic and intermediate to acidic plutonic rocks [1, 7, 8]. Often, they are overlain by fossiliferous Phanerozoic sediments [1, 9]. Consequently, the first to assign a Precambrian age to the g","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139501765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Unloading excavation can increase the possibility of rock burst, especially for coal seam with rock parting. In order to explore the evolution process of rock burst under lateral unloading, the combination of in situ measures and numerical experiments is used to study. The following four points were addressed: (1) the coal seam with rock parting easily causes the stick-slip and instability along the interface, and the process of stick-slip and instability has hysteresis characteristics; (2) the greater the degree of unloading or the smaller the interface friction angle of the Coal-Rock Parting-Coal Structure (CRCS), the more likely it is for stick-slip and instability to occur; (3) the abnormal increase of shear stress and slip dissipation energy can be used as the precursory information of the stick-slip and instability of CRCS; (4) the damage intensity of rock burst induced by stick-slip and instability of CRCS can be reduced by reducing the unloading speed or increasing the roughness of interface. The research results can be used for early warning and controlling of dynamic disaster induced by stick-slip instability in coal seam with rock parking.The slip-staggered rock burst is caused by the slip dislocation of the internal related structure, which mainly occurs in the fault, coal seam separation, and abnormal change area of coal seam dip angle. The coal seam separation is a typical occurrence structure in coal mines of China, which causes the transformation of coal and rock structures, and commonly the Coal-Rock Parting-Coal Structure (CRCS) is formed by rock parting upper and lower coal seams [1, 2]. The natural CRCS is in a stable triaxial stress state. The process of roadway excavation can cause the redistribution of surrounding rock stress and cause the horizontal stress to be gradually released, and the CRCS also changes from a three-dimensional stress state to a lateral unloading state [3-6]. As the interface of coal and rock parting is weak, the process of lateral unloading may cause stick-slip and instability along the weak surface, which easily leads to rock burst accidents.In recent years, with the rapid development of science and technology, the research methods of rock mechanics are gradually enriched. The deformation and failure mechanism of unloading coal/rock mass is gradually revealed, and the mechanism of stick-slip instability of the contact surface is also constantly verified [7]. Such as He et al. [8-10] designed a true-triaxial rock burst test simulation system and simulated the lateral sudden unloading process caused by deep rock excavation. Lu et al. [11] studied the precursory characteristics of rock burst induced by fault stick-slip instability through field observations and biaxial direct shear friction experiments and explained the influence of friction coefficient on stick-slip instability. Liu et al. [12] confirmed that the rock parting structure also has the characteristics of stick-slip and instability under th
{"title":"Numerical Study on Characteristics of Stick-Slip Instability of Coal-Rock Parting-Coal Structure under Lateral Unloading","authors":"Heng Zhang, Guang-Jian Liu, Xian-Jun Ji, Wen-Hao Cao, Ya-Wei Zhu, Sher Bacha","doi":"10.2113/2024/lithosphere_2023_172","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_172","url":null,"abstract":"Unloading excavation can increase the possibility of rock burst, especially for coal seam with rock parting. In order to explore the evolution process of rock burst under lateral unloading, the combination of in situ measures and numerical experiments is used to study. The following four points were addressed: (1) the coal seam with rock parting easily causes the stick-slip and instability along the interface, and the process of stick-slip and instability has hysteresis characteristics; (2) the greater the degree of unloading or the smaller the interface friction angle of the Coal-Rock Parting-Coal Structure (CRCS), the more likely it is for stick-slip and instability to occur; (3) the abnormal increase of shear stress and slip dissipation energy can be used as the precursory information of the stick-slip and instability of CRCS; (4) the damage intensity of rock burst induced by stick-slip and instability of CRCS can be reduced by reducing the unloading speed or increasing the roughness of interface. The research results can be used for early warning and controlling of dynamic disaster induced by stick-slip instability in coal seam with rock parking.The slip-staggered rock burst is caused by the slip dislocation of the internal related structure, which mainly occurs in the fault, coal seam separation, and abnormal change area of coal seam dip angle. The coal seam separation is a typical occurrence structure in coal mines of China, which causes the transformation of coal and rock structures, and commonly the Coal-Rock Parting-Coal Structure (CRCS) is formed by rock parting upper and lower coal seams [1, 2]. The natural CRCS is in a stable triaxial stress state. The process of roadway excavation can cause the redistribution of surrounding rock stress and cause the horizontal stress to be gradually released, and the CRCS also changes from a three-dimensional stress state to a lateral unloading state [3-6]. As the interface of coal and rock parting is weak, the process of lateral unloading may cause stick-slip and instability along the weak surface, which easily leads to rock burst accidents.In recent years, with the rapid development of science and technology, the research methods of rock mechanics are gradually enriched. The deformation and failure mechanism of unloading coal/rock mass is gradually revealed, and the mechanism of stick-slip instability of the contact surface is also constantly verified [7]. Such as He et al. [8-10] designed a true-triaxial rock burst test simulation system and simulated the lateral sudden unloading process caused by deep rock excavation. Lu et al. [11] studied the precursory characteristics of rock burst induced by fault stick-slip instability through field observations and biaxial direct shear friction experiments and explained the influence of friction coefficient on stick-slip instability. Liu et al. [12] confirmed that the rock parting structure also has the characteristics of stick-slip and instability under th","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139689428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-12DOI: 10.2113/2024/lithosphere_2023_320
Yakun Tian, Zhijun Zhang, Min Wang, Lingling Wu, Lin Hu, Rong Gui
The mechanical characteristics of tailing sands have an important impact on the safety and stability of the tailing dams. Fully understanding the effect of drying and wetting cycles (DWC) and water content on the characteristics of tailing sands is urgently needed. In this study, direct shear tests were first carried out to analyze the effect of DWC and water content on the macroscopic mechanical characteristics of tailing sands. Then, the mesoscopic mechanical behavior of tailing sands with different water contents under the action of DWC was studied by using PFC2D particle flow software. The results showed that the effect of DWC on the shear properties of tailing sands is more pronounced than water content. The cohesive force and the internal friction angle increase first and then decrease with the increasing water content. With the increasing number of DWC, the cohesive force and the internal friction angle all decreased to varying degrees. The results of the mesoscopic mechanical analysis indicated that after experiencing the DWC, the force chain of the sample gradually thickens to form a coarse force chain network area, and the number of cracks inside the sample is significantly larger than that of the sample that has not experienced the DWC. The results of this study are of great significance for understanding the macroscopic and mesoscopic shear failure mechanism of tailing sands under the effects of DWCs and water content.The tailing dam is a man-made debris flow hazard with high potential energy, and there are many unstable factors in its operation process. The collapse of the tailing dam not only affects the production of mining enterprises but also brings huge disasters to the inhabitants. Due to periodic changes in water conditions (i.e., rainfall infiltration, water evaporation, and repeated elevation and decline of the infiltration line), the tailing dam is subjected to long-term drying and wetting cycles (DWCs) during operation. It was found that the DWCs will lead to a decrease in the mechanical properties of the soil, and the changes in water content also affect the microstructure and mechanical properties of the soil. Under the action of DWC and water content, the matric suction and shear strength of the soil will change, thus affecting the stability of the soil structure. Therefore, a comprehensive understanding of the influence of the DWC and water content on the characteristics of tailing sands is of great significance for the long-term safety and stability of the tailing dam.A substantial effort has been made on the changes in the physical properties and mechanical behavior of rock materials under the action of cyclic wetting and drying [1-21]. The properties of rock materials (i.e., porosity, longitudinal wave velocity, compressive strength, shear strength, etc.) are significantly influenced by DWCs. Zhou et al. [7] studied the dynamic tensile strength characteristics of rocks after cyclic drying and wetting. They inferred
{"title":"Study of the Effect of Drying and Wetting Cycles and Water Content on the Shear Characteristics of Tailing Sands","authors":"Yakun Tian, Zhijun Zhang, Min Wang, Lingling Wu, Lin Hu, Rong Gui","doi":"10.2113/2024/lithosphere_2023_320","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_320","url":null,"abstract":"The mechanical characteristics of tailing sands have an important impact on the safety and stability of the tailing dams. Fully understanding the effect of drying and wetting cycles (DWC) and water content on the characteristics of tailing sands is urgently needed. In this study, direct shear tests were first carried out to analyze the effect of DWC and water content on the macroscopic mechanical characteristics of tailing sands. Then, the mesoscopic mechanical behavior of tailing sands with different water contents under the action of DWC was studied by using PFC2D particle flow software. The results showed that the effect of DWC on the shear properties of tailing sands is more pronounced than water content. The cohesive force and the internal friction angle increase first and then decrease with the increasing water content. With the increasing number of DWC, the cohesive force and the internal friction angle all decreased to varying degrees. The results of the mesoscopic mechanical analysis indicated that after experiencing the DWC, the force chain of the sample gradually thickens to form a coarse force chain network area, and the number of cracks inside the sample is significantly larger than that of the sample that has not experienced the DWC. The results of this study are of great significance for understanding the macroscopic and mesoscopic shear failure mechanism of tailing sands under the effects of DWCs and water content.The tailing dam is a man-made debris flow hazard with high potential energy, and there are many unstable factors in its operation process. The collapse of the tailing dam not only affects the production of mining enterprises but also brings huge disasters to the inhabitants. Due to periodic changes in water conditions (i.e., rainfall infiltration, water evaporation, and repeated elevation and decline of the infiltration line), the tailing dam is subjected to long-term drying and wetting cycles (DWCs) during operation. It was found that the DWCs will lead to a decrease in the mechanical properties of the soil, and the changes in water content also affect the microstructure and mechanical properties of the soil. Under the action of DWC and water content, the matric suction and shear strength of the soil will change, thus affecting the stability of the soil structure. Therefore, a comprehensive understanding of the influence of the DWC and water content on the characteristics of tailing sands is of great significance for the long-term safety and stability of the tailing dam.A substantial effort has been made on the changes in the physical properties and mechanical behavior of rock materials under the action of cyclic wetting and drying [1-21]. The properties of rock materials (i.e., porosity, longitudinal wave velocity, compressive strength, shear strength, etc.) are significantly influenced by DWCs. Zhou et al. [7] studied the dynamic tensile strength characteristics of rocks after cyclic drying and wetting. They inferred ","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140072332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Magmatic activity in the syn-collision stage is key for net crustal growth. To understand the mechanism of accretion–differentiation and compositional change of the continental crust, it is important to focus on the magmatic activity during the syn-collision stage. Early Eocene mafic–ultramafic rock assemblages found in the western part of the Tengchong Block resulted from a continuous series of arc magmatic evolution, thoroughly recording the continental arc magmatic system during the subduction of the Neo-Tethys Ocean and syn-collision of the Indian-Asian continents. Early Eocene hornblende gabbro–diorite in the Tengchong Block formed at 53 Ma, and the primitive magma was derived from an enriched mantle source due to the enriched Nd–Hf isotopes. The amphibole and biotite thermobarometer measurements indicate that the mafic magma reservoirs in the Tengchong Block occurred at a mid-upper crust. Petrography, amphibole Fe/Mg exchange coefficient (KD), Rayleigh fractionation, and equilibrium melt calculation indicate that the Early Eocene hornblende gabbro–diorite in the Tengchong Block was created due to plagioclase-dominated accumulation at the mid-upper crust level. Based on the calculation, the corresponding amphibole equilibrium melt is more silicic (dacitic–rhyolitic in composition) than the bulk rocks, indicating a more evolved composition in the mid-upper crust. Three types of plagioclases reveal the multi-recharging and dissolution–reprecipitation promoting the further evolution of these mafic rocks. Therefore, this study concludes that magma recharge and plagioclase-dominated accumulation processes may be important mechanisms for the formation and evolution of mafic magma and the further crustal differentiation at the mid-upper crust level in a continental margin arc.Arc is an important region for the growth and differentiation of the continental crust, and arc igneous rock is ideal for understanding the evolution of magma reservoirs and the transcrustal magmatic system in depth. Increasing level of attention is being given to the evolution process and the corresponding mechanism of magmatism in the continental arc [1-6]. However, the andesitic component of the continental crust cannot be completely derived from the single-stage melting of mantle-derived magmas; it requires additional magmatic evolutionary processes. These processes include gradual differentiation of mantle-derived basaltic magmas by fractional crystallization within the upper mantle and lower crust, and/or partial melting of the early mafic crust [1, 2, 7-10]. Recently, studies on the construction and differentiation of the continental crust have focused on the genesis of granite [11-16], whereas the vertical multistage differentiated evolution of mantle magma within the continental crust can be considered as the fundamental process of magmatic evolution from the mafic lower crust to the felsic upper crust [7, 8, 17-19]. The pyroxene-/amphibole-rich mafic intrusive and ac
{"title":"Continental Arc Accumulation Mafic Rocks in the Mid-Upper Crust: Constraints From the Early Eocene Hornblende Gabbro–Diorite in the Tengchong Block, Southeastern Extension of Tibet","authors":"Tai Wen, Shao-wei Zhao, Xiao-yu Fang, Xian-Zhi Pei, Zuo-Chen Li, Jing-Yuan Chen","doi":"10.2113/2024/lithosphere_2023_319","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_319","url":null,"abstract":"Magmatic activity in the syn-collision stage is key for net crustal growth. To understand the mechanism of accretion–differentiation and compositional change of the continental crust, it is important to focus on the magmatic activity during the syn-collision stage. Early Eocene mafic–ultramafic rock assemblages found in the western part of the Tengchong Block resulted from a continuous series of arc magmatic evolution, thoroughly recording the continental arc magmatic system during the subduction of the Neo-Tethys Ocean and syn-collision of the Indian-Asian continents. Early Eocene hornblende gabbro–diorite in the Tengchong Block formed at 53 Ma, and the primitive magma was derived from an enriched mantle source due to the enriched Nd–Hf isotopes. The amphibole and biotite thermobarometer measurements indicate that the mafic magma reservoirs in the Tengchong Block occurred at a mid-upper crust. Petrography, amphibole Fe/Mg exchange coefficient (KD), Rayleigh fractionation, and equilibrium melt calculation indicate that the Early Eocene hornblende gabbro–diorite in the Tengchong Block was created due to plagioclase-dominated accumulation at the mid-upper crust level. Based on the calculation, the corresponding amphibole equilibrium melt is more silicic (dacitic–rhyolitic in composition) than the bulk rocks, indicating a more evolved composition in the mid-upper crust. Three types of plagioclases reveal the multi-recharging and dissolution–reprecipitation promoting the further evolution of these mafic rocks. Therefore, this study concludes that magma recharge and plagioclase-dominated accumulation processes may be important mechanisms for the formation and evolution of mafic magma and the further crustal differentiation at the mid-upper crust level in a continental margin arc.Arc is an important region for the growth and differentiation of the continental crust, and arc igneous rock is ideal for understanding the evolution of magma reservoirs and the transcrustal magmatic system in depth. Increasing level of attention is being given to the evolution process and the corresponding mechanism of magmatism in the continental arc [1-6]. However, the andesitic component of the continental crust cannot be completely derived from the single-stage melting of mantle-derived magmas; it requires additional magmatic evolutionary processes. These processes include gradual differentiation of mantle-derived basaltic magmas by fractional crystallization within the upper mantle and lower crust, and/or partial melting of the early mafic crust [1, 2, 7-10]. Recently, studies on the construction and differentiation of the continental crust have focused on the genesis of granite [11-16], whereas the vertical multistage differentiated evolution of mantle magma within the continental crust can be considered as the fundamental process of magmatic evolution from the mafic lower crust to the felsic upper crust [7, 8, 17-19]. The pyroxene-/amphibole-rich mafic intrusive and ac","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140323688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-12DOI: 10.2113/2024/lithosphere_2023_231
Jesús Díaz-Curiel, Bárbara Biosca, Lucía Arévalo-Lomas, David Paredes-Palacios, María J. Miguel
This study first reviews the influence of grain size on the permeability of porous granular media in comparison to other factors, especially the sorting of grain size distribution, in order to improve the physical knowledge of permeability. The aim of this research is to counter the widespread misconception that the characteristics of water flow in granular porous media can be associated exclusively with an area regarding grain size. This review involves two different aspects. First, the dependence of the intrinsic permeability on the particle size distribution is highlighted, independently of the other internal factors such as porosity and average grain size, by simply reviewing the main existing formulas. Second, the historical literature on the influence of the average grain size in porosity is analyzed, and it is compared with the influence of the granulometric sorting. The most recognized data show that the influence of each of these two factors is of the same order, but it was not expressed in mathematical form, so a relationship of porosity versus average grain size and sorting is established. The two aforementioned steps conclude that the factors influencing permeability do not advise the use of area dimensions because it leads to only link permeability with the average grain size, especially when nonspecialists come into contact with earth sciences. Finally, after a review of the historical evolution of the permeability units, they are redefined to avoid the common misconception that occurs when the established unit leads to only a partial understanding of the key parameters influencing permeability.Historically, permeability characterizes all types of porous solid media, focusing this work on granular media, where permeability is a key petrophysical parameter due to its application in many fields of Earth sciences, such as hydrogeology, oil field, geological environment, geotechnics, and soil science in agronomy.As initially established by Darcy [1], permeability is the ease with which water can move through pore spaces in porous media. The flow velocity of water depends on the internal characteristics of the medium and the pressure gradient to which it is subjected; however, considering the rigidity of the solid phase, in granular media, this flow velocity depends on the pressure gradient to which the water is subjected [2].Over time, the concept of permeability long included the influence of temperature, which was first recognized at the same time as the concept of fluid viscosity [3, 4]. In this way, by including the fluid viscosity in the relationships to obtain permeability, a process to generalize the Darcy equation to the flow of any fluid was initiated. However, this process implied the separation of two very distinct aspects affecting the measurable flow velocity, the internal characteristics of the medium, and the characteristics of the fluid. Despite this, the term permeability was maintained up to 1940 to characterize flow i
{"title":"On the Influence of Grain Size Compared with Other Internal Factors Affecting the Permeability of Granular Porous Media: Redefining the Permeability Units","authors":"Jesús Díaz-Curiel, Bárbara Biosca, Lucía Arévalo-Lomas, David Paredes-Palacios, María J. Miguel","doi":"10.2113/2024/lithosphere_2023_231","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_231","url":null,"abstract":"This study first reviews the influence of grain size on the permeability of porous granular media in comparison to other factors, especially the sorting of grain size distribution, in order to improve the physical knowledge of permeability. The aim of this research is to counter the widespread misconception that the characteristics of water flow in granular porous media can be associated exclusively with an area regarding grain size. This review involves two different aspects. First, the dependence of the intrinsic permeability on the particle size distribution is highlighted, independently of the other internal factors such as porosity and average grain size, by simply reviewing the main existing formulas. Second, the historical literature on the influence of the average grain size in porosity is analyzed, and it is compared with the influence of the granulometric sorting. The most recognized data show that the influence of each of these two factors is of the same order, but it was not expressed in mathematical form, so a relationship of porosity versus average grain size and sorting is established. The two aforementioned steps conclude that the factors influencing permeability do not advise the use of area dimensions because it leads to only link permeability with the average grain size, especially when nonspecialists come into contact with earth sciences. Finally, after a review of the historical evolution of the permeability units, they are redefined to avoid the common misconception that occurs when the established unit leads to only a partial understanding of the key parameters influencing permeability.Historically, permeability characterizes all types of porous solid media, focusing this work on granular media, where permeability is a key petrophysical parameter due to its application in many fields of Earth sciences, such as hydrogeology, oil field, geological environment, geotechnics, and soil science in agronomy.As initially established by Darcy [1], permeability is the ease with which water can move through pore spaces in porous media. The flow velocity of water depends on the internal characteristics of the medium and the pressure gradient to which it is subjected; however, considering the rigidity of the solid phase, in granular media, this flow velocity depends on the pressure gradient to which the water is subjected [2].Over time, the concept of permeability long included the influence of temperature, which was first recognized at the same time as the concept of fluid viscosity [3, 4]. In this way, by including the fluid viscosity in the relationships to obtain permeability, a process to generalize the Darcy equation to the flow of any fluid was initiated. However, this process implied the separation of two very distinct aspects affecting the measurable flow velocity, the internal characteristics of the medium, and the characteristics of the fluid. Despite this, the term permeability was maintained up to 1940 to characterize flow i","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139500801","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Different scales of fractures affect the reservoir quality in tight sandstone. There are more studies on macroscopic tectonic fractures but less on bedding fractures and microfractures. The control factors of multi-scale fractures are unclear. In this paper, we analyzed the types and controls of fractures in the second member of the Xinchang region in Western Sichuan. We use core and outcrops observations, imaging logging, scanning energy spectra, and rock slices. Natural fractures can be classified into tectonic, bedding, and microscopic types. The tectonic fractures are mainly low- to medium-angle tensile fractures. The bedding fractures are nearly horizontally distributed along the bedding surface, including parallel, dark mineral interface, and carbonaceous fragments interface bedding fractures. The microfractures develop intra-grain, edge-grain, and inter-grain types. The intra-grain microfractures are inside quartz or feldspar grains, whereas inter-grain types penetrate multiple grains with larger extension lengths. The tectonic fractures are related to the stress, grain size, mineral component, argillaceous content, and lithologic thickness. Parallel bedding fractures are controlled by the coupling of water depth and flow velocity. Bedding fractures at the interface are controlled by rock component. The microfractures are controlled by the length-width axis ratio of the grain, grain element content, and brittleness index. Fractures of different scales form a three-dimensional fracture system that has a substantial impact on the gas production.Tight sandstone gas is an unconventional natural resource dominated by low-porosity and low-permeability reservoirs with porosity less than 10% and air permeability less than 1 × 10–3 μm2 [1-4]. It has been discovered in many basins in China [5-8] and accounts for a relatively large proportion of the gas production, such as in the Ordos, Sichuan, Junggar, and Tarim basins [9-16]. The Xinchang gas field in the Sichuan Basin was first discovered in 1988. The exploration progress was slow owing to the insufficient understanding of geological and fracking processes. After 2,000 years, a few exploration wells were drilled in close to the fracture system, and gas production was increased [17-21]. Exploration showed that the fractures play an important role in controlling the gas production of the Xinchang gas field. However, the distribution of fractures in this zone is complex with different fracture geneses, scales, and occurrences. Nevertheless, there is a lack of the systematic understanding of fractures.Tectonic fractures in tight sandstones have been extensively studied [22, 23]. The factors affecting them include the stress heterogeneity in different tectonic zones [24-31] and lithologic heterogeneity [32-34]. Sedimentation controls differences in the lithology and layer thickness, and heterogeneity in the mineral composition and structure of reservoirs influence fracture development [35-40]. Bedding
{"title":"Controls of Multi-Scale Fractures in Tight Sandstones: A Case Study in the Second Member of Xujiahe Formation in Xinchang Area, Western Sichuan Depression","authors":"Junwei Zhao, Yingtao Yang, Gongyang Chen, Xiaoli Zheng, Senlin Yin, Lei Tian","doi":"10.2113/2024/lithosphere_2023_343","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_343","url":null,"abstract":"Different scales of fractures affect the reservoir quality in tight sandstone. There are more studies on macroscopic tectonic fractures but less on bedding fractures and microfractures. The control factors of multi-scale fractures are unclear. In this paper, we analyzed the types and controls of fractures in the second member of the Xinchang region in Western Sichuan. We use core and outcrops observations, imaging logging, scanning energy spectra, and rock slices. Natural fractures can be classified into tectonic, bedding, and microscopic types. The tectonic fractures are mainly low- to medium-angle tensile fractures. The bedding fractures are nearly horizontally distributed along the bedding surface, including parallel, dark mineral interface, and carbonaceous fragments interface bedding fractures. The microfractures develop intra-grain, edge-grain, and inter-grain types. The intra-grain microfractures are inside quartz or feldspar grains, whereas inter-grain types penetrate multiple grains with larger extension lengths. The tectonic fractures are related to the stress, grain size, mineral component, argillaceous content, and lithologic thickness. Parallel bedding fractures are controlled by the coupling of water depth and flow velocity. Bedding fractures at the interface are controlled by rock component. The microfractures are controlled by the length-width axis ratio of the grain, grain element content, and brittleness index. Fractures of different scales form a three-dimensional fracture system that has a substantial impact on the gas production.Tight sandstone gas is an unconventional natural resource dominated by low-porosity and low-permeability reservoirs with porosity less than 10% and air permeability less than 1 × 10–3 μm2 [1-4]. It has been discovered in many basins in China [5-8] and accounts for a relatively large proportion of the gas production, such as in the Ordos, Sichuan, Junggar, and Tarim basins [9-16]. The Xinchang gas field in the Sichuan Basin was first discovered in 1988. The exploration progress was slow owing to the insufficient understanding of geological and fracking processes. After 2,000 years, a few exploration wells were drilled in close to the fracture system, and gas production was increased [17-21]. Exploration showed that the fractures play an important role in controlling the gas production of the Xinchang gas field. However, the distribution of fractures in this zone is complex with different fracture geneses, scales, and occurrences. Nevertheless, there is a lack of the systematic understanding of fractures.Tectonic fractures in tight sandstones have been extensively studied [22, 23]. The factors affecting them include the stress heterogeneity in different tectonic zones [24-31] and lithologic heterogeneity [32-34]. Sedimentation controls differences in the lithology and layer thickness, and heterogeneity in the mineral composition and structure of reservoirs influence fracture development [35-40]. Bedding","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140017254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-12DOI: 10.2113/2024/lithosphere_2023_216
Yu Zhang, Xu Zhao, Fei Guo, Lianjin Tao, Jun Liu, Weizhang Liao, Lei Tan, Xiaohui Yang
In pipe jacking engineering, accurate prediction of jacking force is the key to pipe jacking design. Based on a project of the Beijing Daxing Airport Line, the influence of the advance jacked pipes on the jacking force of the subsequent pipe is carried out in the present work. First, the verified numerical model of practical engineering was established, and the jacking force and radial stress of different pipes were analyzed. Then, the two pipes were taken as research object, and the parameters of spacing, angle, buried depth, and pipe diameter were investigated, respectively. The results show that in the actual project, the advance jacked pipes have amplification and superposition effects on friction resistance of the subsequent pipe, and the maximum growth rate is 37.2%. The friction resistance of the subsequent pipe presents a trend of first increasing and then decreasing with the change of the layout angle of advance jacked pipe from 0° to 180°. With the increase of buried depth and pipe diameter, the absolute value of incremental friction resistance of the subsequent pipe increases gradually, but the growth rate remains constant. Finally, the empirical formulas for predicting the friction resistance growth rate of subsequent pipes under different angles are proposed. The research results can provide some reference for the design of pipe jacking.In recent years, rapid urbanization resulted in a great development in underground space. The pipe jacking method has been widely used in energy transportation engineering, water conservancy, and tunnel engineering because of its advantages of fast construction speed, little disturbance to the surrounding environment, and easy-to-control jacking accuracy [1-12]. Besides, pipe jacking is also used in pipe roof engineering. For example, the Xinle Ruin station of Shenyang subway line 2 was built with the pipe roof method. The pipe roof structure consists of 19 steel pipes with a diameter of 2000 mm and 2 steel pipes with a diameter of 2300 mm [13]. The Gongbei tunnel was built by 36 steel pipes with a diameter of 1620 mm [14].The core problem of pipe jacking is still the calculation of friction resistance. The magnitude of the jacking force is directly determined by the friction resistance, and the radial stress of the pipe–soil interface determines the distribution and magnitude of friction resistance stress. At present, the existing literatures have done a lot of research on the friction resistance. The numerical simulation and laboratory test methods have been adopted to study the pipe–soil interaction under different types of lubricants and their combinations by Shou et al. [15]. They concluded that the reduction of the jacking force is closely related to the decrease of friction coefficient, and the effect of lubrication is slightly more significant in the case of curved pipe than in the case of linear pipe. Yen and Shou [16] took the obtained average friction coefficient as the input parameter of t
{"title":"Influence of the Advance Jacked Pipe on the Jacking Force of the Subsequent Pipe Based on Pipe–Soil Full Contact Model","authors":"Yu Zhang, Xu Zhao, Fei Guo, Lianjin Tao, Jun Liu, Weizhang Liao, Lei Tan, Xiaohui Yang","doi":"10.2113/2024/lithosphere_2023_216","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_216","url":null,"abstract":"In pipe jacking engineering, accurate prediction of jacking force is the key to pipe jacking design. Based on a project of the Beijing Daxing Airport Line, the influence of the advance jacked pipes on the jacking force of the subsequent pipe is carried out in the present work. First, the verified numerical model of practical engineering was established, and the jacking force and radial stress of different pipes were analyzed. Then, the two pipes were taken as research object, and the parameters of spacing, angle, buried depth, and pipe diameter were investigated, respectively. The results show that in the actual project, the advance jacked pipes have amplification and superposition effects on friction resistance of the subsequent pipe, and the maximum growth rate is 37.2%. The friction resistance of the subsequent pipe presents a trend of first increasing and then decreasing with the change of the layout angle of advance jacked pipe from 0° to 180°. With the increase of buried depth and pipe diameter, the absolute value of incremental friction resistance of the subsequent pipe increases gradually, but the growth rate remains constant. Finally, the empirical formulas for predicting the friction resistance growth rate of subsequent pipes under different angles are proposed. The research results can provide some reference for the design of pipe jacking.In recent years, rapid urbanization resulted in a great development in underground space. The pipe jacking method has been widely used in energy transportation engineering, water conservancy, and tunnel engineering because of its advantages of fast construction speed, little disturbance to the surrounding environment, and easy-to-control jacking accuracy [1-12]. Besides, pipe jacking is also used in pipe roof engineering. For example, the Xinle Ruin station of Shenyang subway line 2 was built with the pipe roof method. The pipe roof structure consists of 19 steel pipes with a diameter of 2000 mm and 2 steel pipes with a diameter of 2300 mm [13]. The Gongbei tunnel was built by 36 steel pipes with a diameter of 1620 mm [14].The core problem of pipe jacking is still the calculation of friction resistance. The magnitude of the jacking force is directly determined by the friction resistance, and the radial stress of the pipe–soil interface determines the distribution and magnitude of friction resistance stress. At present, the existing literatures have done a lot of research on the friction resistance. The numerical simulation and laboratory test methods have been adopted to study the pipe–soil interaction under different types of lubricants and their combinations by Shou et al. [15]. They concluded that the reduction of the jacking force is closely related to the decrease of friction coefficient, and the effect of lubrication is slightly more significant in the case of curved pipe than in the case of linear pipe. Yen and Shou [16] took the obtained average friction coefficient as the input parameter of t","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139951551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-12DOI: 10.2113/2024/lithosphere_2023_302
Danqing Song, Xuerui Quan, Zhuo chen, Dakai Xu, Chun Liu, Xiaoli Liu, Enzhi Wang
To investigate the dynamic response and attenuation law of rock slope sites subjected to blasting, three lithological numerical models, including slate (hard rock), tuff (relatively soft rock), and shale (soft rock), are established by using MatDEM. By analyzing the wave field, velocity, and acceleration response of the models and their Fourier spectrum, combined with stress and energy analysis, their dynamic response characteristics are investigated. The results show that blasting waves propagate from near field to far field in a circular arc, and the attenuation effect of waves in soft rock is less than that in hard rock. The influence of lithology on the dynamic response of the ground surface and bedrock is different. Blasting waves mainly affect the dynamic response in the near-field area of the blasting source. In addition, the dynamic amplification effect of slopes is as follows: hard rock > relatively soft rock > soft rock. The slope surface has an elevation attenuation effect. A dynamic amplification effect appears in the slope interior within the relative elevation (0.75, 1.0). The Fourier spectrum has an obvious predominant frequency, and that of the slope crest and interior is less than that of the slope surface. Moreover, the total energy generated by the rocky sites gradually changes into kinetic energy, gravitational potential energy, elastic potential energy, and heat. Energy-based analysis shows that the attenuation effect of blasting waves in hard rock is larger than that in soft rock overall. This work can provide a reference for revealing the blasting vibration effect of rock sites.Because of the advantages of fast construction, low cost, and high efficiency, the blasting method has become the main construction method of slope and tunnel engineering [1]. Nevertheless, due to the influence of the propagation medium, the waveforms and propagation characteristics of blasting seismic waves become very complicated [2]. Blasting seismic waves will lead to slope instability and other geological disasters; in particular, in coal mining areas, under the influence of human blasting over the years, geological disasters, such as mountain cracking and creep, will occur on slopes, seriously threatening the safety of people’s lives and property [3, 4]. Moreover, seismic exploration blasting technology is an important method in geophysical exploration [5]. The seismic effect of explosive blasting has become a key problem in land oil and gas exploration and foundation construction. The propagation law and damage effect of seismic waves in different geological bodies are the main basis of engineering blasting design [6, 7]. Therefore, explosion-induced seismic waves have been one of the most active subjects in the field of civil engineering blasting.Blasting seismic waves are a complex physical phenomenon [8, 9]. It is affected by many factors, such as the location of the source of detonation, the amount of explosive, the mode of explosion, the
{"title":"Influence of Lithology on the Characteristics of Wave Propagation and Dynamic Response in Rocky Slope Sites Subject to Blasting Load Via the Discrete Element Method","authors":"Danqing Song, Xuerui Quan, Zhuo chen, Dakai Xu, Chun Liu, Xiaoli Liu, Enzhi Wang","doi":"10.2113/2024/lithosphere_2023_302","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_302","url":null,"abstract":"To investigate the dynamic response and attenuation law of rock slope sites subjected to blasting, three lithological numerical models, including slate (hard rock), tuff (relatively soft rock), and shale (soft rock), are established by using MatDEM. By analyzing the wave field, velocity, and acceleration response of the models and their Fourier spectrum, combined with stress and energy analysis, their dynamic response characteristics are investigated. The results show that blasting waves propagate from near field to far field in a circular arc, and the attenuation effect of waves in soft rock is less than that in hard rock. The influence of lithology on the dynamic response of the ground surface and bedrock is different. Blasting waves mainly affect the dynamic response in the near-field area of the blasting source. In addition, the dynamic amplification effect of slopes is as follows: hard rock > relatively soft rock > soft rock. The slope surface has an elevation attenuation effect. A dynamic amplification effect appears in the slope interior within the relative elevation (0.75, 1.0). The Fourier spectrum has an obvious predominant frequency, and that of the slope crest and interior is less than that of the slope surface. Moreover, the total energy generated by the rocky sites gradually changes into kinetic energy, gravitational potential energy, elastic potential energy, and heat. Energy-based analysis shows that the attenuation effect of blasting waves in hard rock is larger than that in soft rock overall. This work can provide a reference for revealing the blasting vibration effect of rock sites.Because of the advantages of fast construction, low cost, and high efficiency, the blasting method has become the main construction method of slope and tunnel engineering [1]. Nevertheless, due to the influence of the propagation medium, the waveforms and propagation characteristics of blasting seismic waves become very complicated [2]. Blasting seismic waves will lead to slope instability and other geological disasters; in particular, in coal mining areas, under the influence of human blasting over the years, geological disasters, such as mountain cracking and creep, will occur on slopes, seriously threatening the safety of people’s lives and property [3, 4]. Moreover, seismic exploration blasting technology is an important method in geophysical exploration [5]. The seismic effect of explosive blasting has become a key problem in land oil and gas exploration and foundation construction. The propagation law and damage effect of seismic waves in different geological bodies are the main basis of engineering blasting design [6, 7]. Therefore, explosion-induced seismic waves have been one of the most active subjects in the field of civil engineering blasting.Blasting seismic waves are a complex physical phenomenon [8, 9]. It is affected by many factors, such as the location of the source of detonation, the amount of explosive, the mode of explosion, the ","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139690006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-12DOI: 10.2113/2024/lithosphere_2023_317
Zeqi Zhu, Xiancheng Mei, Jianhe Li, Qian Sheng
In order to study the initiation mechanism of rocks under hydromechanical coupling, hydromechanical coupling triaxial tests and acoustic emission tests were carried out on basalt in the Xiluodu hydropower station dam site area in southwestern China. The test results indicate that the basalt displays typical hard brittle behavior, and its peak strength increases as confining pressure rises. Conversely, the peak strength decreases gradually as the initial water pressure increases, which leads to decreased hardness. Meanwhile, tensile failure is the main crack initiation mode under hydromechanical coupling action. During the stable crack growth stage, tensile failure is predominant, complemented by shear failure, with failures mainly occurring in the rock middle position. Contrary to this, during the unstable stage, the rock failure is mainly due to shear failure. The critical pore water pressure failure criterion of rock crack initiation under hydromechanical coupling conditions is derived based on the test results and introduced into the numerical simulation. The hydromechanical coupling failure process and pore water pressure distribution law of basalt are analyzed, and the rationality of the critical pore water pressure failure criterion is verified. These findings are significant for understanding the rock failure process under hydromechanical coupling action and provide a valuable reference for future research.Hydroelectric engineering projects often involve structures such as underground power stations, water diversion tunnels, and sloping dam foundations, which are subjected to the combined action of high-ground stress and strong osmotic pressure. Therefore, research on the mechanical properties of rocks or rock masses under hydromechanical coupling has become a pressing issue in geotechnical engineering. Several scholars, including Song et al. [1], Zhu et al. [2], Yu et al. [3], Xu et al. [4], Wang et al. [5], and Wang et al. [6], have conducted hydromechanical coupling triaxial tests on limestone [1-3], sandstone [4-6], and granite [7, 8] to investigate the relationship between rock permeability, stress, strain, and pore water pressure. They have discussed the influence of pore water pressure on rock strength characteristics, deformation laws, and damage evolution. Moreover, Li et al. [9], Zhao [10], and Guo et al. [11] have employed acoustic emission (AE) signals to analyze the AE characteristics during the process of rock cracking under hydromechanical coupling.The aforementioned research has extensively demonstrated that hydromechanical coupling induces pore water pressure within the internal cracks of a rock, which significantly impacts the cracking process [12, 13]. Once the pore water pressure attains a critical level, it instigates the inception, expansion, and penetration of rock cracks, commonly referred to as hydromechanical fracturing [14]. This phenomenon is a significant factor that causes a range of engineering disasters, inc
{"title":"Experimental and Numerical Investigation of Rock Failure Process under Hydromechanical Coupling Action","authors":"Zeqi Zhu, Xiancheng Mei, Jianhe Li, Qian Sheng","doi":"10.2113/2024/lithosphere_2023_317","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_317","url":null,"abstract":"In order to study the initiation mechanism of rocks under hydromechanical coupling, hydromechanical coupling triaxial tests and acoustic emission tests were carried out on basalt in the Xiluodu hydropower station dam site area in southwestern China. The test results indicate that the basalt displays typical hard brittle behavior, and its peak strength increases as confining pressure rises. Conversely, the peak strength decreases gradually as the initial water pressure increases, which leads to decreased hardness. Meanwhile, tensile failure is the main crack initiation mode under hydromechanical coupling action. During the stable crack growth stage, tensile failure is predominant, complemented by shear failure, with failures mainly occurring in the rock middle position. Contrary to this, during the unstable stage, the rock failure is mainly due to shear failure. The critical pore water pressure failure criterion of rock crack initiation under hydromechanical coupling conditions is derived based on the test results and introduced into the numerical simulation. The hydromechanical coupling failure process and pore water pressure distribution law of basalt are analyzed, and the rationality of the critical pore water pressure failure criterion is verified. These findings are significant for understanding the rock failure process under hydromechanical coupling action and provide a valuable reference for future research.Hydroelectric engineering projects often involve structures such as underground power stations, water diversion tunnels, and sloping dam foundations, which are subjected to the combined action of high-ground stress and strong osmotic pressure. Therefore, research on the mechanical properties of rocks or rock masses under hydromechanical coupling has become a pressing issue in geotechnical engineering. Several scholars, including Song et al. [1], Zhu et al. [2], Yu et al. [3], Xu et al. [4], Wang et al. [5], and Wang et al. [6], have conducted hydromechanical coupling triaxial tests on limestone [1-3], sandstone [4-6], and granite [7, 8] to investigate the relationship between rock permeability, stress, strain, and pore water pressure. They have discussed the influence of pore water pressure on rock strength characteristics, deformation laws, and damage evolution. Moreover, Li et al. [9], Zhao [10], and Guo et al. [11] have employed acoustic emission (AE) signals to analyze the AE characteristics during the process of rock cracking under hydromechanical coupling.The aforementioned research has extensively demonstrated that hydromechanical coupling induces pore water pressure within the internal cracks of a rock, which significantly impacts the cracking process [12, 13]. Once the pore water pressure attains a critical level, it instigates the inception, expansion, and penetration of rock cracks, commonly referred to as hydromechanical fracturing [14]. This phenomenon is a significant factor that causes a range of engineering disasters, inc","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139553739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qiongdongnan Basin (QDNB), located at the northwestern corner of the South China Sea (SCS), is a key juncture between the extensional tectonic regime in the northern continental margin and the shear tectonic regime in the western continental margin. Analyzing the crustal density structure and tracking the thermodynamic controlling factors are effective approaches to reveal the nonuniform breakup process of the northwestern SCS. Herein, focusing on the obvious tectonic deformation with distinct eastern and western parts in the QDNB, we present the crustal density structures of five profiles and identify the high-density anomaly related to the synrifting mantle underplating and postrifting magmatic intrusions. The crustal density model was constructed from the Bouguer gravity anomaly, ocean bottom seismic profiles, and multichannel seismic reflection profiles. The northern part of QDNB, with normal crustal density, lower surface heat flow of <55 mW/m2, and limited extension factor of 1.25–1.70, is recognized as the initial nonuniform extension continental crust. The mantle underplating beneath the QDNB is identified as a high mantle density of 3.30–3.40 g/cm3 and a high lower crustal density of 2.92–2.96 g/cm3, which is usually recognized by the high-velocity layers in the northeastern margin of SCS. The magmatic intrusions are identified as the high-density bodies ranging from 3.26 g/cm3 at the base to 2.64 g/cm3 at the top, which become stronger from the west to east. The central part of Xisha Trough is featured by the cooling of the heavily thinned lower crust in the final continental rifting stage, which is close to the cold and rigid oceanic crust. Lateral variations in the deep magmatic anomaly should be the crucial factor for the nonuniform breakup process in the northwestern margin of SCS.As the largest Cenozoic marginal basin located in the western Pacific region, the South China Sea (SCS) was formed in a complex tectonic setting due to the strong interaction among the Indo-Australian, Eurasian, and Pacific plates [1, 2] (Figure 1). Because of the stretching stress introduced by the rollback of the paleo-Pacific plate and the slab pull of the paleo-SCS, the SCS shows the ununiform continental rifting and progressive seafloor spreading from east to west, featuring highly inhomogeneous crustal structure and asymmetric magmatism beneath the marginal basins [3-5]. It is generally accepted that the SCS might represent a “plate-edge or Pacific-type” extensional basin, and the passive upwelling of the fertile asthenospheric mantle induced by the surrounding subductions could be primarily responsible for these inhomogeneous features [6, 7]. Some scholars even believed that the SCS had experienced a “magma-rich”-type breakup process in its middle-eastern part, but a “magma-poor” one is observed in the west [4, 8].In the case of the northern continental margin of SCS, the compositional or structural east–west heterogeneity has been observed by vario
{"title":"Gravity-Seismic Joint Inversion of Lithospheric Density Structure in the Qiongdongnan Basin, Northwest South China Sea","authors":"Chaoyang Li, Wei Gong, Lihong Zhao, Zhonghua Li, Pengyao Zhi, Jiayu Ge","doi":"10.2113/2024/lithosphere_2023_124","DOIUrl":"https://doi.org/10.2113/2024/lithosphere_2023_124","url":null,"abstract":"Qiongdongnan Basin (QDNB), located at the northwestern corner of the South China Sea (SCS), is a key juncture between the extensional tectonic regime in the northern continental margin and the shear tectonic regime in the western continental margin. Analyzing the crustal density structure and tracking the thermodynamic controlling factors are effective approaches to reveal the nonuniform breakup process of the northwestern SCS. Herein, focusing on the obvious tectonic deformation with distinct eastern and western parts in the QDNB, we present the crustal density structures of five profiles and identify the high-density anomaly related to the synrifting mantle underplating and postrifting magmatic intrusions. The crustal density model was constructed from the Bouguer gravity anomaly, ocean bottom seismic profiles, and multichannel seismic reflection profiles. The northern part of QDNB, with normal crustal density, lower surface heat flow of <55 mW/m2, and limited extension factor of 1.25–1.70, is recognized as the initial nonuniform extension continental crust. The mantle underplating beneath the QDNB is identified as a high mantle density of 3.30–3.40 g/cm3 and a high lower crustal density of 2.92–2.96 g/cm3, which is usually recognized by the high-velocity layers in the northeastern margin of SCS. The magmatic intrusions are identified as the high-density bodies ranging from 3.26 g/cm3 at the base to 2.64 g/cm3 at the top, which become stronger from the west to east. The central part of Xisha Trough is featured by the cooling of the heavily thinned lower crust in the final continental rifting stage, which is close to the cold and rigid oceanic crust. Lateral variations in the deep magmatic anomaly should be the crucial factor for the nonuniform breakup process in the northwestern margin of SCS.As the largest Cenozoic marginal basin located in the western Pacific region, the South China Sea (SCS) was formed in a complex tectonic setting due to the strong interaction among the Indo-Australian, Eurasian, and Pacific plates [1, 2] (Figure 1). Because of the stretching stress introduced by the rollback of the paleo-Pacific plate and the slab pull of the paleo-SCS, the SCS shows the ununiform continental rifting and progressive seafloor spreading from east to west, featuring highly inhomogeneous crustal structure and asymmetric magmatism beneath the marginal basins [3-5]. It is generally accepted that the SCS might represent a “plate-edge or Pacific-type” extensional basin, and the passive upwelling of the fertile asthenospheric mantle induced by the surrounding subductions could be primarily responsible for these inhomogeneous features [6, 7]. Some scholars even believed that the SCS had experienced a “magma-rich”-type breakup process in its middle-eastern part, but a “magma-poor” one is observed in the west [4, 8].In the case of the northern continental margin of SCS, the compositional or structural east–west heterogeneity has been observed by vario","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139553743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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